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Subject: Re: 2.6.33.3-rt19 kernel BUG's
From: john stultz <johnstul@us.ibm.com>
To: Fernando Lopez-Lezcano <nando@ccrma.Stanford.EDU>
Cc: Thomas Gleixner <tglx@linutronix.de>, LKML <linux-kernel@vger.kernel.org>,
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Date: Mon, 10 May 2010 13:02:41 -0700
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On Mon, 2010-05-10 at 10:11 -0700, Fernando Lopez-Lezcano wrote:
> On Fri, 2010-05-07 at 17:39 -0700, john stultz wrote:
> > On Fri, 2010-05-07 at 23:58 +0000, Fernando Lopez-Lezcano wrote:
> > > On Fri, 2010-05-07 at 16:43 -0700, john stultz wrote:
> > > > On Fri, 2010-05-07 at 12:41 +0200, Thomas Gleixner wrote:
> > > > > On Thu, 6 May 2010, Fernando Lopez-Lezcano wrote:
> > > > > 
> > > > > CC'ed John and Nick
> > > > > 
> > > > > > See below... just trying to boot (quad core desktop machine).
> > > > 
> > > > Ok. Got this to reproduce. Will hopefully have a fix for your soon.
> > > > 
> > > > Thanks for the bug report!
> > > 
> > > Thanks for looking at it! It had been a while since I had problems with
> > > rt so I could not understand why I could not login :-) 
> > 
> > Bah! I should have caught this faster. I kept thinking it had to be some
> > missed unlock of the sbi->fs_lock, but it ends up its just the
> > autofs4_lock.
> > 
> > Apparently the conversion from using the dcache_lock -> autofs4_lock
> > forgot that this function already grabs the autofs_lock for a small
> > moment, so we end up grabbing the lock, then a moment later grab it
> > again. Splat.
> > 
> > This patch should resolve it.
> 
> I'm still having problems when trying to use autofs, even with your
> previous patch:

Oof.. More of the same autofs4_lock misuse.  I skimmed over the rest of
its use, and it seems ok,  so hopefully we won't hit any more problems
caused by it.

Here's both autofs4_lock changes together.

Signed-off-by: John Stultz <johnstul@us.ibm.com.

diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
index 5b26088..40ca936 100644
--- a/fs/autofs4/root.c
+++ b/fs/autofs4/root.c
@@ -317,7 +317,6 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
 	 * multi-mount with no root mount offset. So don't try to
 	 * mount it again.
 	 */
-	spin_lock(&autofs4_lock);
 	spin_lock(&dentry->d_lock);
 	if (ino->flags & AUTOFS_INF_PENDING ||
 	    (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs))) {
@@ -438,12 +437,10 @@ static int autofs4_revalidate(struct dentry *dentry, struct nameidata *nd)
 	}
 
 	/* Check for a non-mountpoint directory with no contents */
-	spin_lock(&autofs4_lock);
 	if (S_ISDIR(dentry->d_inode->i_mode) &&
 	    !d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
 		DPRINTK("dentry=%p %.*s, emptydir",
 			 dentry, dentry->d_name.len, dentry->d_name.name);
-		spin_unlock(&autofs4_lock);
 
 		if (autofs4_need_mount(flags) || current->link_count) {
 			int status;